The present invention relates to a display module, a manufacturing method thereof, and a display device using the display module.
Conventionally, there are self-luminous light emitting elements such as a light emitting diode (LED), an organic electroluminescence (EL) element, an inorganic EL element, and non-self-luminous light emitting elements such as a liquid crystal.
A self-luminous light emitting element array is constituted by arranging a plurality of self-luminous light emitting elements two-dimensionally in a matrix. A display device using the self-luminous light emitting element array exhibits lower optical loss and higher light use efficiency, as compared with a light-valve type display device such as a liquid crystal display. When the self-luminous light emitting element array is employed in a direct-view-type display device, the direct-view-type display device can be lightened and thinned, since a backlight can be eliminated.
Further, a projection type display device such as a head up display (HUD), a projector or a rear projector using the non-self-luminous type light emitting elements needs a separate light source. In contrast, a projection type display device using the self-luminous type light emitting element array does not need such a separate light source, and therefore can be compact in size.
In this regard, for example, when the HUD has a display magnification of 5 times, the HUD utilizes light emitted within an angle of 10-20 degrees (i.e., an available angle) from a direction of an optical axis of the light emitting element. However, light emitted by the self-luminous light emitting element array (in which the light emitting elements are arranged in a plane) has a basically Lambertian distribution, and therefore light use efficiency is as low as 3-5%.
In order to enhance light use efficiency of the HUD, it is conceivable to form a microlens array on the light emitting element array to thereby narrow a spread of light, i.e., to increase an amount of light within the available angle. In this case, it is necessary to form an On-Chip microlens array on the light emitting element array, and a lens material (i.e., a material of the microlens array) need be removed from regions of bonding pads.
Japanese Laid-open Patent Publication No. 2006-327182 discloses a method of forming an On-Chip microlens array on the light emitting element array using a glass forming mold, and patterning the microlens array using exposure and development.
However, in the conventional method, the display module is manufactured by forming the microlens array using the glass forming mold, and transferring the microlens array onto the self-luminous light emitting element array. In the transfer process, it is difficult to accurately align the microlens array with the self-luminous light emitting element array. Further, since it is necessary to ensure releasability of the glass forming mold, and to provide a spacer for maintaining a gap between the microlens array and the self-luminous light emitting element array in the direction of the optical axis, the number of manufacturing processes increases.